Turkish warplanes have carried out airstrikes on sites believed to be used by US-backed Kurdish militant groups in northern Syria after the US military shot down an armed Turkish drone that came within 500 metres of American troops.

A Turkish defence ministry statement said the Turkish jets targeted some 30 sites in the Tal Rifat, Jazeera and Derik regions, destroying caves, bunkers, shelters and warehouses used by Kurdistan Workers’ Party, PKK, or its affiliated Kurdish militia group in Syria, which is known as People’s Defence Units, or YPG.

Turkey has been carrying out strikes on Kurdish militant targets in Iraq and Syria following a suicide attack outside the interior ministry building in the Turkish capital earlier this week.

The PKK claimed the attack in which one attacker blew himself up and another would-be bomber was killed in a shootout with police. Two police officers were wounded.

Turkish foreign minister Hakan Fidan said the two assailants had arrived from Syria, where they had been trained. He said PKK and YPG positions in Iraq and Syria had now become legitimate targets.

Kurdish authorities in north-east Syria said on Thursday evening that Turkish bombing had struck 21 sites and 11 people were killed by the “Turkish aggression” — five civilians and six members of the local government’s internal security forces.

The US-backed and Kurdish-led Syrian Democratic Forces in north-east Syria have denied any relationship to the Ankara attack and accused Turkey of using the attack as a pretext for a new military incursion.

In Washington, the Pentagon said on Thursday that the Turkish drone bombed targets near the US troops in Syria, forcing them to go to bunkers for safety.

Air Force Brigadier General Patrick Ryder, the Pentagon press secretary, said the decision to shoot down the drone of a Nato ally “was made out of due diligence and the inherent right of self-defence to take appropriate action to protect US forces”.

There was no indication that Turkey was intentionally targeting US forces, he said.

Turkey’s Foreign Ministry on Friday blamed the downing of the drone on conflicting evaluations of what it called a “de-escalation mechanism” operated between the sides.

Necessary measures were being taken to ensure a “more effective operation” of the mechanism, the ministry said without elaborating.

“The incident did in no way affect the execution of the ongoing operation and the strikes against targets that were identified,” the ministry said.

Both defence secretary Lloyd Austin and the new joint chiefs chairman, General CQ Brown, spoke with their Turkish counterparts quickly after the incident to emphasise the value they place on their relationship with Turkey — but also the need to avoid any similar incidents in the future and ensure the safety of US personnel.

The US has about 900 troops in Syria conducting missions to counter Islamic State group militants.